Method transform

packages/common/src/pipes/number_pipe.ts:279–314

(
    value: number | string | null | undefined,
    currencyCode: string = this._defaultCurrencyCode,
    display: 'code' | 'symbol' | 'symbol-narrow' | string | boolean = 'symbol',
    digitsInfo?: string,
    locale?: string,
  )

    locale?: string,
  ): string | null;
  transform(
    value: number | string | null | undefined,
    currencyCode: string = this._defaultCurrencyCode,
    display: 'code' | 'symbol' | 'symbol-narrow' | string | boolean = 'symbol',
    digitsInfo?: string,
    locale?: string,
  ): string | null {
    if (!isValue(value)) return null;

    locale ||= this._locale;

    if (typeof display === 'boolean') {
      if (typeof ngDevMode === 'undefined' || ngDevMode) {
        console.warn(
          `Warning: the currency pipe has been changed in Angular v5. The symbolDisplay option (third parameter) is now a string instead of a boolean. The accepted values are "code", "symbol" or "symbol-narrow".`,
        );
      }
      display = display ? 'symbol' : 'code';
    }

    let currency: string = currencyCode || this._defaultCurrencyCode;
    if (display !== 'code') {
      if (display === 'symbol' || display === 'symbol-narrow') {
        currency = getCurrencySymbol(currency, display === 'symbol' ? 'wide' : 'narrow', locale);
      } else {
        currency = display;
      }
    }

    try {
      const num = strToNumber(value);
      return formatCurrency(num, locale, currency, currencyCode, digitsInfo);
    } catch (error) {
      throw invalidPipeArgumentError(CurrencyPipe, (error as Error).message);
    }
  }
}

function isValue(value: number | string | null | undefined): value is number | string {